Anabolic steroids, the synthetic variants of the primary masculinizing androgen testosterone, are abused by growing numbers of individuals in this country ranging from adolescents seeking to improve their appearance to professional athletes attempting to elevate their performance. The specific aim of the present research is to provide preliminary information on the causes and consequences of such abuse in humans by investigating their effects in laboratory mice. Physical dependence will be studied by exploring behavioral and physiological reactions to both acute and chronic anabolic steroid administration. In addition, we will explore withdrawal symptoms (e.g., the abstinence syndrome) following the termination of chronic treatment as well as the reversal of withdrawal symptoms following readministration of anabolic steroids. Behavioral dependence will be analyzed by studying whether or not and to what extent anabolic steroid hormones can produce pleasurable subjective states with such states having the potential to control behavior. Specifically, Pavlovian conditioning techniques (e.g., context conditioned place preference) will be utilized to explore the issue of behavioral dependence. Finally, because increases in aggressive behavior and violence are some of the most frequently reported side effects of anabolic steroid abuse in humans, we will examine the extent to which anabolic steroid hormones can promote species-typical aggressive behavior in mice. The findings ultimately will aid us in understanding the potential addictive nature and adverse behavioral consequences of these hormones.